Marking up with layers

Putting a reference behind something in the plate.

The common job is showing an artist what should be where. Say a mountain belongs behind the trees.

1. Park on the frame and open ▤ Layers.
2. 🖼 Reference and pick the mountain image. It lands centred.
3. With ✥ Move, drag it into position and scale it by the corner handle.
4. Lower its opacity to check the fit against the plate.
5. Take 🪣 Erase reference and brush the mountain away across the trees — the real trees come back through, and the mountain now sits behind them.
6. Overshot an edge? 🖌 Restore reference paints that patch back.
7. Add a T text box naming the change, then Save sketch.

Nothing is destructive: the source image is untouched and the mask is a set of paths you can delete.